1. Field of the Invention
The subject invention relates to a mount assembly for a vehicle having a frame and a vehicle body wherein movements of the frame relative to the vehicle body are isolated and/or translated by an insulator.
2. Description of Related Art
Mount assemblies for vehicles are well known in the art. Examples of such assemblies are shown in U.S. Pat. Nos. 6,361,096 and 6,416,102. Each of these assemblies includes a support structure mounted to a frame and a carrier mounted to a vehicle body. The carrier is coupled to the support structure through one or more insulators. The insulators are typically formed of an elastomeric material such as rubber or microcellular polyurethane (MPU).
Currently the insulators are characterized using a load verses deflection curve. An example of such a curve is shown in FIG. 7. The prior art rubber R and prior art urethane C are illustrated along side the subject invention. The slope of the curve represents the effective spring rate. A lower slope represents a softer spring and a higher slope represents a stiffer or harder spring. Vibrational motion is generally associated with lower forces, amplitudes and higher frequencies and is isolated better with softer springs. Translational motion on other hand is associated with lower frequencies, and larger forces which create maximum displacements. When using linear springs this causes large relative displacement at maxiumum loads. It is desirable to have the insulators operate at lower or softer spring rates to allow for improved isolation of vibrations of the support structure relative to the carrier such that the vehicle body is cushioned on the frame. In order to achieve the desired performance, the insulators are formed of a low modulus material and have a relatively large height. The relatively tall insulators, however, require large clearances between the carrier and the support structure. This also creates an undesirable large displacement between the carrier and the support structure which equates to an undesirable large movement (maximum displacement) between the frame and the vehicle body. Many conventional rubber insulators are a compromise between lower or softer spring rates and maxiumum displacement. In addition, many of the conventional insulators cannot be adequately customized or tuned because of the material and geometrical limitations.
Cylinderical or annular insulators made of mircocellular material can provide the soft spring rate as well as some maximum displacement control. However the total maximum displacement is still too large and the nature and location of the transition from soft to hard spring rate cannot be controlled independent of the properties of polymer. And thus is not easily tunable.
Accordingly, it would be desirable to develop an insulator that is of a reasonable height, takes advantage of a low or soft spring rate, and has low maximum displacement and is easily tunable or customizable.